Deflecting and focusing device for cathode-ray apparatus



March 21, 1950 H. c. HOLDEN 2,501,516 DEFLECTING AND FOCUSING DEVICE FORCATHODE RAY APPARATUS Filed Dec. 31, 1947 2 Sheets-Sheet 1 Inventor:Harold C. H olden,

His Attorney.

March 21, 1950 H. c. HOLDEN DEFLECTING AND FOCUSING DEVICE FOR CATHODERAY APPARATUS Filed Dec. 31, 1947 VII/1 VIIIIIIIIII$ 2 Sheets-Sheet 2lhvehtor: Harold C. Holden,

by m%- Wm His Attorney.

Patented Mar. 21, 1950 UNITED STATES PATENT 'QFFHCE DEFLECTING ANDFOCUSING DEVICE FOR CATHODE-RAY APPARATUS Harold C. Holden, Bridgeport,Conn., assignor to General Electric Company, a corporation of New York 4Claims.

My invention relates to devices for deflecting and focusing cathode raybeams in electron discharge devices of the cathode ray type and hasparticular application to cathode ray tubes for television receivers.

In television receivers and similar apparatus it is desirable to providesome arrangement for centering and adjusting the cathode ray beam in thepicture tube and for aligning the horizontal and vertical axes of thepicture. Such adjustment makes it possible to replace the tube andadjust the new tube satisfactorily without the necessity of providing anew tube which is so constructed that it produces its cathode ray beamin the exact location of that produced by the replaced tube. Relativelycomplicated mountings have been provided for this purpose heretofore.Accordingly it is an object of my invention to provide an improvedadjustable beam deflecting and focusing arrangement for electrondischarge devices of the cathode ray type.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My inventionitself, however, both as to its organization and method of operation,together with further objects and advantages thereof, may best beunderstood by reference to the following description taken in connectionwith the accompanying drawings in which Fig. 1 is a side elevation view,partly illustrated in Fig. 1 includes an electron dis charge device Iwhich is of the cathode ray type commonly used for the reproduction ofpictures in television receivers. The device is provided with a glassenvelope comprising a bowl portion 2, only; a part of which is shown inthe drawing, and an;

elongated cylindrical neck 3. The envelope is supported on suitablebrackets 4 and 5, the bracket 5 being provided with an adjustable collar5 clamped about the neck 3. The device I may have as an additionalsupport a clamping arrangement (not shown) which is positioned abouttheedge portion of the bowl 2 adjacent the usual,

fluorescent screen on which the picture is reproduced. Within the neck 3near the end remote from the bowl 2 there is provided the usual cathoderay beam forming device commonly called an electron gun an anode portionof which is indicated generally at I. The construction and arrangementof the electron gun to produce a cathode ray beam is well known and adetailed description is not necessary to an understanding of the presentinvention. The electron beam is projected along the axis of the neck 3onto the fluorescent screen and produces a spot of light at the point atwhich it impinges on the screen. In order to focus the spot of lightupon the screen, a focusing yoke 8 is mounted about the envelope 3 nearthe source of the electron beam. The yoke 8 produces a magnetic fieldwhich constitutes a magnetostatic lens for concentrating the beam ofelectrons. As illustrated, the yoke 8 comprises a coil 9 arranged withina hollow ring of magnetic material comprising an inner cylinder l0, anouter cylinder It and an end member I 2, the outer cylinder ll beingformed to provide the opposite end member. The inner cylinder in isspaced from the outer cylinder H at its inner periphery to provide anannular air gap 13, the magnetost-atic lens being formed generally inthe plane of the air gap so that the center of the lens coincides withthe longitudinal axis of the coil 9. The focusing of the beam iseffected by adjusting the excitation of the coil 9 which is suppliedwith direct current from a suitable source (not shown).

In order to produce the television picture which requires horizontal andvertical deflection of the cathode ray beam in a manner which is wellunderstood in the art, a deflecting coil assembly I4 is mounted aboutthe neck 3 between the bowl 2 and the focusing yoke 8. The televisionpicture is produced by modulating the intensity of the beam while it isbeing deflected over the surface of the screen so that the intensity ofany given area of the screen corresponds with that of the transmittedpicture of that area. The yoke 8 is supported within the bracket 4 andis rotatable about theneck 3 on a nonmagnetic sleeve l5 which isrotatably fitted in an opening [5 in the bracket 4 and is retained inplace by a plurality of spring clips l1; one of which is shown. Thedeflecting coil assembly I4 is rotatably mounted with respect to thebracket 4 on a circular plate 18 held in an annular retaining shoulder19 formed on the bracket and retained in place frictionally by aplurality of spring clamps 20 only one of which has been illustrated onthe drawing. The plate l8 and the endportion of the assembly M arespaced from the sleeve l5 so that the sleeve 3 and the assembly may eachbe rotated in the bracket 4 independently.

It is impractical to provide television receivers which are so adjustedat the factory that no further adjustment or servicing is necessary inorder to center the picture on the screen. Furthermore, the cathode raytubes employed for television receivers are not identical so that whenit becomes necessary to replace a tube it is also necessary to readjustthe focusing and deflecting devices to secure the desired position ofthe picture. In the apparatus illustrated, this adjustment can beaccomplished by first rotating the reflecting coils l4 about theenvelope 3 until the edges of the rectangular picture are parallel totheir desired final positions. The spring clamps then retain thedeflecting coils in their required positions. The next step in adjustingthe picture is to move the center of the picture until it coincides withits required center position. This is accomplished by rotating andtilting the focusing yoke 8 in a manner to be described.

The yoke 8 is mounted on the sleeve 15 on two spring arms 21 attached byscrews 22 to opposite sides of the yoke. The arms 2i extend axially ofthe yoke within the cylinder H3 and are provided with pivots 23 whichengage diametrically opposite holes 25 in the sleeve l5, as clearlyshown in Fig. 2. The spring arms take up any slack or endplay in thepivot members and, since the pivots 23 are located so that the pivotalaxis passes substantially through the center of the magnetostatic lens,tilting of the yoke produces little shifting of the lens center andmaintains the center of the lens substantially on the axis of theelectron gun regardless of the tilt of the yoke. After the electron beamhas been focused by adjusting the strength of the magnetic field asdetermined by the excitation of the focusing coil El, and after correctalignment of the picture by adjustment of the deflecting-coils l 4, thefocusing yoke 8 is rotated on the collar 15 about the neck 3 until theaxis of the pivots 23 is at right angles to a line passing through thecenters of the picture in its incorrect position and in its desiredposition. It will now be apparent that the picture can be centeredmerely by tilting the yoke until the center points coincide. The tiltingis accomplished by adjusting a wing nut 25 threaded on a stud 26 whichis attached to an extension 27 on the sleeve l5 and passes through a lug28 attached to the outer cylinder ll of the yoke 8. bracket 4 isprevented by a compression spring 28 arranged about the stud 26 betweenthe bracket and lug 28. It is thus apparent that the entire adiustinentnecessary may be made simply by rotation of the deflecting assembly l4about the envelope 3, rotation of the yoke 8 with the sleeve [5, andtilting of the yoke by adjustment of the wing nut 25.

Referring now to Fig. 3, I have illustrated a deflecting and focusingassembly embodying my invention and in which a permanent magnet focusingyoke an is employed. The yoke and a deflecting coil assembly 3! arerotatably mounted on a neck 32 of a cathode raytube 33 of the same typeas the tube I of Fig. 1. The yoke 53! is secured directly to a sleeve 34by screws 35 and the sleeve 34 fits about the neck 32, a suitableintermediate or spacing sleeve 36 of felt or other suitable materialbeing provided so that the sleeve 34 may readily be rotated about theglass envelope. The yoke 3| includes a casing or shell 31 and thefocusing and deflecting assembly'is Lost motion between the lug 28 androtatably secured within a support 38 which is provided with a circularopening 39 rotatably engaging a boss 40 on the shell 37. A flange M onthe sleeve 34 prevents axial movement of the deflecting and focusingassembly in the opening 39. lhis flange may be resilient to providespring pressure for retaining the assembly in position on the support.The deflecting coil assembly 3|, as shown in Fig. l, comprises a squaremagnetic core 42 on which are arranged two sets of deflecting coils 43,a: for providing deflecting fields at right angles to one another. Thecasing 37 is of square cross section and is closed by a cap 45 having acircular opening provided with a suitable resilient gasket 46 engagingthe neck 32 of the tube adjacent the bowl indicated at 41. The cap 45thus encloses the yoke and coils within the casing 31. The yoke 42 issecured within the casing 31 on four corner pieces 48 which are weldedor otherwise secured in position and are provided with rectangularopenings for receiving the corners of the yoke, as clearly indicated inFig. 6, which illustrates one of the corner pieces 45% showing theopening .at 39 and the position of the core 42, as indicated in .dot anddash lines. It will thus be seen that the deflecting coil assembly 3imay readily be rotated within the support 38 about the envelope 32 sothat the cathode ray beam generated by the usual electron gun, the anodeof which is indicated at 58, may be defiected along the desired paths.

The permanent magnet focusing yoke 36 comprises a permanent magnet inthe form of a cylinder or ring 5| and two pole pieces 52 and 53 formingwith the magnet 5! a hollow ring provided with an annular air gap 55between the pole pieces 52 and 53. The yoke 30 is pivotally mounted on asleeve 55 which is slidably mounted on the sleeve 36 so that it may berotated and moved axially along the sleeve 13%. The yoke fill isprovided with two diagonally opposite spring arms 56 secured to the yokeby screws 57 remote from the air gap 54. The spring arms 56 extendaxially of the yoke 30 and cross the air gap 54, and pivot members ortrunnions 58 are secured in the ends of the spring arms and areJ'ournaled in bearings 59 in the sleeve 55. It will thus be apparentthat the yoke '30 can be moved axially of the sleeve 32, rotatedthereon, and tilted with respect thereto along the axis of the pivots58. The axial movement of the yoke is necessary in order to adjust theeffect of the magnetostatic lens on the cathode ray beam since it is notpossible to adjust the strength of the permanent magnet in a mannersimilar to the adjustment of the field strength by changing theexcitation of the coil 9 of the yoke in Fig. 1. Except for the differentmethod for focusing the beam, the adjust ment of the deflecting andfocusing yoke of the apparatus shown in Fig. 3 is the same as that ofthe apparatus shown in Fig. 1, the edges of the picture first being madeparallel with their required positions and the yoke thereafter beingtilted to bring the center of the aligned picture into coincidence withthe required center for the picture.

The positioning of the yoke pivots in the plane of the air gap so thatthe pivotal axis passes substantially through the center of themagnetostatic lens insuring minimum shifting of the center of the lenswhen focusing yoke is tilted to center the picture. The mounting of theyokes on spring arms provides an arrangement for taking up end-play inthe pivots and facilitates the as- 76 sembly of the yoke.

From the foregoing it is readily apparent that I have provided asimple-and easily adjusted arrangement for securin the properpositioning of the deflecting coils and focusing yoke so that thepicture presented on the screen of an electron discharge device of thecathode ray type may be made to appear in its required position.Although I have illustrated and described specific arrangementsembodying m invention, modifications will occur to those skilled in theart. I do not, therefore, desire my invention to be limited to theparticular constructions illustrated and I intend by the appended claimsto cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In an electron discharge apparatus of the cathode ray type includingan envelope having therein a screen and an electron gun for projecting acathode ray beam onto the screen, a support, .a magnetic deflecting coilattached to said support and mounted about said envelope between saidgun and said screen, a magnetic focusing yoke for providing a,magnetostatic lens in the path of said beam, said yoke being attached tosaid support and mounted about said envelope near the origin of saidbeam, said coil and said yoke both being rotatable relative to eachother and to said support and said envelope about the axis of said beam,the mounting for said yoke including pivot members positioned in theplane of said lens whereby the direction of said beam may be adjusted.

2. In an electron discharge apparatus of the cathode ray type includingan envelope having a screen and an electron gun for projecting a cathoderay beam onto the screen, a support, a sleeve rotatably mounted aboutsaid envelope and rotatably secured to said support, a magneticdeflecting coil mounted on said support for rotation about the axis ofsaid beam and arranged about said envelope between said gun and saidscreen, a magnetic focusing yoke for providing a magnetostatic lens inthe path of said beam, said yoke being mounted about said envelope nearthe neticideflecting' coil mounted about said envelope bet en said gunand said screen, a magnetic ing yoke comprising a magnetic shell in the"of a hollow ring having an annular air gap the inner wall thereof forproviding a magestatic lens in the path of said beam, a sleeve atablyfitted about said envelope, and means hiding axially extending springarms secured id shell remote from said air gap and having pivot membersengaging said sleeve in the plane pfsaid air gap for mounting said yokeon said sleeve to aiford tilting of the central axis of said lens withrespect to the central axis of said envelope whereby the direction ofsaid beam may 5b adjusted.

In an electron discharge apparatus of the cathode ray type including anenvelope having therein'a screen and an electron gun for projectng acathode ray beam onto the screen, a sleeve netic deflecting coil mountedon said sleeve and arranged about said envelope between said gun roatably mounted about said envelope, a ma and said screen, a secondsleeve rotatably and slidably mounted on said first sleeve, a magneticfocusing yoke for providing a, magnetostatic lens in the path of saidbeam, said yoke being mounted about said envelope near the origin ofsaid beam and being secured pivotally to said second sleeve Q forrotation about said envelope with respect to located on a transverseaxis passing substantially said coil, the pivotal mountin for said yokebeing through the center of said lens normal to the central axisthereof.

HAROLD C. HOLDEN.

, file of this patent:

origin of said beam and being secured pivotally therein a screen and anelectron gun for project- I ing a cathode ray beam onto the screen, amag- UNITED STATES PATENTS Number Name Date 2,234,720 Detar Mar. 11,1941 2,416,687 Fry Mar. 4, 1947 2,418,487 Sproul Apr. 8, 1947 2,428,928Cain Oct. 14, 1947 2,431,077 Jackson Nov. 18, 1947 2,435,613 Sproul Feb.10, 1948 2,440,403 Pooh Apr. 27, 1948 2,456,399 Gethmann Dec. 14, 1948FOREIGN PATENTS Number Country Date 472,165 Great Britain Sept. 13, 1937523,439 Great Britain July 15, 1940

